As is known, electrostatic filters for the filtration of air provide for the passage of such air through an ionization zone or section, comprising a high-potential polarizing electrode in which the suspended solid particles are electrostatically charged, and for the passage of such ionized particles via routes delimited by walls charged with opposite sign to that of the particles, which are thereby attracted to the said walls on which they settle in a stable manner.
Such electrostatic filters may be substantially of two types: so-called single-stage filters in which the ionization section and the collecting section are combined in a single section, and so-called two-stage filters in which the two sections are separated and placed in succession to one another, each section having its own electric field. In both cases, the filter may be of single-body type, that is, consisting of a single unit housing both sections, or of dual-body type, that is, with the components comprising the two sections being physically different and capable of being separated from one another. Within the field of two-stage filters there are known filters of both single-body type and dual-body type which, however, have very limited structural geometries and are difficult to adapt to the different filtering capacities required in different applications, in addition to which their manufacture is extremely laborious and specialized, with high costs of assembly of the parts.
A further constraint of the filters of known type lies in the fact that for normal washing operations it is necessary to remove the ionizing electrode, thus increasing the risk of breakage, and in that a short-circuit even in a limited zone would adversely affect the performance of the entire filter which would effectively be fully short-circuited. There is therefore posed the technical problem of providing a two-stage filter capable of being made from a minimum number of readily assemblable parts and with a geometrical configuration capable of being achieved and/or modified in a very simple manner in relation to the specific requirements of individual applications. The filter should furthermore be simple and inexpensive to construct and assemble, easily applicable to purification equipment and capable of making it possible to achieve the most constant possible performance in time with low maintenance, while also reducing the damage caused by the handling of the ionizing electrode.